The invention relates generally to a computerized system for decision making. More particularly, the present invention relates to the real time system for determining itineraries for public transportation systems which are optimal based upon the rider's criteria.
The problem faced by many riders of public transportation systems is that of choosing or determining a route between an origin and a destination. The public transit rider wishes to choose the optimum itinerary for each trip. Often times, many potential riders would like to use public transportation systems, however, they have difficulty determining the exact location of the transit stations, as well as the route to take to get to their destination.
Once a rider has selected public transportation as the optimum transportation mode, the passenger wishes to maximize his utilization of that system by choosing the optimal set of bus and rail routes through the transit system from his origin to the destination at a particular time of day. While different riders have different objectives and, therefore, different utility functions, virtually all passengers place a high value on travel time.
As is well known, a transit system is a public transportation provider which operates vehicles on fixed routes, according to fixed schedules. An urban transit system typically includes buses and rail vehicles moving along fixed routes and stopping at a predetermined set of transit stations or bus stops. Generally, service is provided in both directions along the route. For convenience, the transit authority designates one of the directions inbound and the other outbound. The transit authority publishes a schedule that lists some or all of the stops along the route, with the times that a vehicle on the route arrives at the stop. Such points listed on the schedule are termed time points. The times for stops not listed on the schedule are determined by interpolation. Typically, a schedule lists several running times for each route.
In addition, certain stops in the transit network are transfer points. Two or more routes service those stops and the transit authority allows transfers between at least two of the routes. In many transit networks, the transit authority will not allow transfers that could be used to make a round trip. Therefore, passengers must request a transfer pass on the first route, so that the transit authority can control which route combinations represent valid transfers. The transfer authority may also require transfer passengers to take the very next bus that passes the transfer stop, in order to prevent passengers from visiting two destinations for a single fare. However, a reasonable amount of time must be allowed between alighting from one transit vehicle and embarkment on the next transit vehicle, so that the transfer is possible even when the vehicles run ahead of or behind schedule.
As described above, the transit system normally follows a predetermined schedule. However, that schedule may be changed relatively frequently, for a number of different reasons. For example, holidays and special events may interrupt the service schedule, or cause it to be temporarily rerouted. Construction of the roads travelled by the transit system and of the transit facilities themselves may also cause interruptions. Also, transit vehicle drivers and other transit workers are typically represented by labor unions that demand service changes three to four times per year.
The problem faced by riders who must choose a route between an origin and a destination is known as the transit itinerary selection problem. Since travellers typically also seek to minimize the amount of walking required at their origins or destinations, the number of transfers required during the trip and the travel itself, passengers typically try to maximize utility by choosing the itinerary having a minimum net travel impedance. When a transit system is modeled as a network, with edge costs measured in units of impedance, the transit itinerary selection problem becomes a shortest path problem. If the impedence of the edges varies with the time of day, it becomes a time-dependent shortest path problem.
In solving the shortest path problem, a network contains a single source node and one or more goal nodes. The problem to be solved is to find a path of minimum length from the source node to a goal node. In addition to solving the shortest path problem in a transportation system, it is desirable to determine the time-dependent shortest path.
Each edge cost is associated with an edge cost function which, for a transit itinerary problem, as with airline scheduling problems and other shortest-path problems where a timetable is involved, is assumed to be a discrete function. Thus, arrival time is determined by looking up the destination nodes entry in a timetable.
For many years, riders or potential riders seeking information with regard to routes typically communicated by telephone with an information agent at the local public transportation company. Such transportation agents, who typically are highly trained and may be long time employees of the public transportation system, are very knowledgeable with regard to the routes and timetables of their transportation company. However, sometimes the agents need to refer to books of route maps and timetables in order to answer incoming queries.
Transit information, however, is relatively complicated. Agents must remember schedules, routes, times, inbound or outbound direction, stop locations, addresses, intersections, landmarks, time of day and whether it is rush hour or not, fares and transfer points. Such data, among other pieces of information, must be remembered by the information agent and related to the caller. While individuals who have been information agents for a long period of time generally have such information at their fingertips, it is much more difficult for less experienced agents. In addition, the process for training new information agents is time consuming and lengthy.
The training of agents is only one of the problems that needs to be solved in order to provide timely and accurate information to a caller in a minimum amount of time. Since most callers to a transit information center ask for detailed trip itineraries, an information agent can spend as much as 8 or even 17 minutes a call with each caller. In addition, some callers are potential new riders who are unsure of their route and may call back again with the same questions. If a different agent gives a different answer, even though correct, not only does the transit system lose the amount of time the agent has spent with the caller, twice, but, may also lose the potential rider who doesn't trust the accuracy of the transit information.
Therefore, there is a need in the art for a computerized information system which can be easily learned by information agents in a short period of time and which provides consistent answers for the information agents to provide to the callers. Since each caller is a potential rider, each caller represents potential additional revenue for the transit system. Therefore, it is desirable to be able to answer all incoming calls in a timely manner and to provide correct and repeatable information to the callers in a very short real-time basis.
Therefore, using the instant inventive system, the productivity of the information agents is increased since the length of each call decreases, the number of calls processed per day increases, and the call capture rate increases. The quality of the information provided is accurate and consistent, is up to the minute, and serves to encourage new riders for the transit system. Also, the instant automated telephone information system is easy to learn and reduces training time to hours. Therefore, part-time or temporary personnel can be used in order to supplement the normal staff of information agents, on an as needed basis.
Using the instant invention, time-consuming cross-referencing of routes and schedules is eliminated and the information agent is therefore able to spend more time interacting with the caller. Because calls are shorter, more of them can be handled by the same number of agents with the same number of telephone lines.
For a further discussion of the need for telephone information transit systems, the reader is referred to Cutler, M. R. and Potter, R. F., The Effectiveness of Telephone Information Services Transit, U.S. Department of Transportation, Urban Mass Transportation Administration, February, 1984.